This invention relates to an automatic weld flaw detector which scans a weld with a probe for flaw detection and records the presence and location of any such flaw detected, all in automatic operation.
Where a conventional ultrasonic flaw detector of the pulse type is used to detect any flaw in a weld and determine its location, as illustrated in FIG. 1, its angle-beam probe P is caused to travel in zigzag fashion on a surface along and parallel to the weld so as to scan the joint thoroughly. In locating a detected flaw F, as shown in FIG. 2, the time axis of the ultrasonic detector is calibrated in advance so that the distance X between the point of incidence of the beam of ultrasonic waves upon the metal surface and the flaw F being detected can be directly read out. Also, the distance Y between the centerline 1 of the weld W and the point of incidence is measured. Then, from the known angle of refraction 0, the distance Z in the direction of depth of the flaw and the distance y from the centerline 1 of the weld W are calculated.
Although the flaw F present in the weld W may be located in the manner described, the procedure when followed manually would necessitate complicated calculation or even in automatic operation would require too large a calculating arragement, such as an electronic computer, to be practical. For the reasons stated, it has been customary, in automatic flaw detection, to record only the presence of any flaw detected and leave the location of the defect unreported.
However, knowing the location of a flaw in the weld is very important because the information will tell the type of the defect and furnish a basis for further evaluation. In addition, it will provide utmost ease of correction of the weld, if necessary.